The present invention relates generally to improved brushes used for surface conditioning. More specifically, the present invention relates to a power brush having an improved tube assembly system. The present invention also relates to an improved power brush adapter that permits the power brush to accommodate a variety of mounting shaft sizes and also permits the shaft to provide positive transmission of torque to the power brush.
High speed rotary brushing is well known as a means for surface conditioning, particularly for metallic objects, and is suitable in a diverse array of applications in areas such as the automotive, farm, and hardware industries. Brushing is an effective technique for cleaning a surface, altering a surface finish, and limited material removal. Brushing permits surface roughening as well as surface smoothing as for deburring or radiusing. The use of a rotary power brush on an object results in a surface with generally uniform scratches, and this surface finish is often acceptable for a given application. Objects that require a scratch-free surface may be subjected to a variety of secondary polishing operations in order to achieve the desired surface finish, such as buffing the object with a cloth wheel charged with a polishing rouge. Brushing is typically accomplished by manually bringing a workpiece in contact with the rotating power brush, or conversely by bringing the power brush in contact with the workpiece. In more sophisticated operations, the brushing task may be automated.
Brush construction features can directly impact the expected brush service life and performance level. Generally, the more rigid and structurally solid a power brush is constructed, the finer the surface finish and the longer the service life of the power brush. A dynamically-balanced power brush assembly transmits less vibration to the equipment and the workpiece, thereby providing enhanced performance.
An important design consideration for a rotary power brush is the choice of central hub construction. Because power brushes generate heat during operation, effective means for heat dissipation must be provided. Metal hub assemblies, which have large contact areas with the mounting shaft, permit thermal conduction from the power brush through the hub and mounting shaft, facilitating heat dissipation.
Filament density, or the number of working filament tips per unit area (commonly referred to as points per square inch), impacts performance as well. Increasing brush filament density results in a finer, more uniform surface finish. A denser-filled brush is more aggressive to the work-piece due to reduced filament flexibility as well as increased working points in contact with the surface per brush revolution. Increased brush filament density also provides longer brush life. Brush filament density can be increased by adding more fill material to an existing design or by reducing the ratio of brush section outside diameter to brush section inside diameter. Brushes having smaller individual filament diameters tend to follow the contours of the workpiece more closely and to produce a more uniform surface, whereas as the density of filaments increases, the brush loses some of its ability to follow contours. Finer diameter filaments are less aggressive toward the workpiece and may result in longer cycle times.
The modern approach to designing and manufacturing power brushes typically involves combining individual, narrow sections together to form a wider face width, thereby producing a generally consistent brush filament density over a large area. Typically, power brushes are formed by mounting a plurality of brush sections on an arbor tube and then mounting a face plate at each end of the arbor tube to maintain the brush sections therebetween. Each brush section is formed by wrapping the brush filaments (e.g., wires) about a retaining ring (which may resemble a washer). The filaments are typically held in place about the retaining ring by friction, such as through the use of an eyelet, so that welding or use of adhesives is not necessary. Once the face plates are positioned at each end of the arbor tube, surrounding the brush sections, the ends of the arbor tube are flanged over the face plates, such as through the use of a hydraulic press which cold-works the material, to secure the face plates in place on the arbor tube. But, internal friction between the component parts and minor variations in section thickness result in a finished power brush assembly with an overall thickness that varies with each power brush produced. In particular, the brush sections are not necessarily brought together in a uniform manner from finished brush to finished brush. Thus, although the number of filaments on each retaining ring typically is set, and the number of brush sections mounted on the arbor tube is set, the stacking of the brush sections against one another and the distance between the face plates is not readily controllable. Accordingly, the packing of the brush sections, and hence the density of the brush filaments of the finished power brush may vary from brush to brush. Thickness variations on the order of 75 to 100 thousandths of an inch may occur potentially resulting in uneven cleaning action may be imparted to a workpiece due to the variation in brush packing.
While the above-described rotary power brush developments permit a rotary power brush to be produced with a reliable construction, it is desirable to manufacture an improved rotary power brush with a structure that provides a more consistent brush filament density.
Certain operating factors also can significantly impact brushing quality and service life. In particular, a more secure connection of the power brush to the drive shaft results in a better surface finish, longer brush service life, and reduced vibration and chatter which cause surface imperfections. Furthermore, by minimizing relative motion between the internal components of the power brush, decreased component wear and degradation are realized.
In rotating machinery, torque may be transmitted from shafts to coupling hubs (or vice versa) through keys, friction, or a combination thereof. A solid connection must be maintained between the driving and the driven components in such a mechanical power transmission system in order to achieve satisfactory performance. Because keyed designs typically are not used in power brush equipment, a relatively tight fit is desirable to achieve frictional engagement to drive the power brush. A true interference fit would contribute to the transmission of torque and also would help to prevent the hub from rocking on the shaft. However, a tight interference fit is not desirable because of the difficulty users experience with changing or removing power brushes from shafts. Thus, coupling hubs, such as arbor tubes, instead are generally installed on shafts with a small amount of clearance to facilitate installation and removal. To secure the power brush on the drive shaft more securely and to prevent relative rotation, a drive flange is clamped on either side of the power brush to engage the face plates of the power brush frictionally so that the power brush may be driven by friction. Such clamping further maintains a secure connection between the power brush and the associated shaft, particularly because keyed systems have not been used between the shaft and arbor tube.
An example of suitable means for holding and centering grinding and polishing wheels or the like on a drive shaft is disclosed in U.S. Pat. No. 1,584,835 to Sven Blanch. The grinding wheels include a central ring that has a passage therethrough which is larger than any arbor on which it is likely to be placed. To center the wheels on arbor tubes of different diameters, a set of two sheet metal discs of the same size is provided, with one disc fitting on each side of the passage through the central ring. Each disc is provided with an annular projection having a cylindrical shoulder that fits the inner wall of the passage through the central ring. The discs also include a central cylindrical wall that forms a bearing for the arbor tube. Sets of discs with different passage diameters permit any wheel to be put on any arbor by selecting the proper pair of discs. Although the discs accommodate a variety of shaft sizes, the discs do not ensure positive torque transmission from the shaft to the disc, and from the disc to the central ring of the wheel assembly.
Modem power brushes are typically provided with an arbor hole of 2 inches in diameter, thereby accommodating shafts with a 2 inch outer diameter. Some power brush assemblies, however, may even include arbor holes of 5 inches or larger in outer diameter. In order to use these power brushes with smaller-sized shafts, adapters may be inserted into the arbor holes. The adapters can permit an operator to use the power brush with shafts that range in size, for example, from xe2x85x9c inch to 1xc2xe inches. One pair of adapters is typically required, with an adapter fitted in either side of the arbor hole.
It therefore would be desirable to provide a brush assembly with a rigid construction and mounting, and a carefully fabricated central hub through which shafts are passed. In addition, it would be desirable to establish a more secure connection of the hub of a power brush assembly to a rotating drive shaft. This is particularly challenging in light of the variety of shaft sizes typically used. It would be desirable to provide a more secure engagement for adapters than currently achieved by frictional engagement. In particular, it would be desirable to achieve a reliable, positive torque transmission from the shaft to the adapter to the central hub of the power brush assembly. Furthermore, it would be desirable to form a power brush assembly which permits the various adapters presently available to fit into the cylindrical arbor hole of the power brush assembly by positive mechanical interlocking.
In accordance with the principles of the present invention, a hub for supporting and retaining at least one surface conditioning article relative to and spaced apart from a rotary shaft is provided. The hub includes an arbor tube having first and second ends, and a pair of face plates each having an inner rim with a top surface and a bottom surface. The arbor tube includes a pair of opposing shoulders, with a shoulder being disposed at each end of the arbor tube. The face plates are coupled to the first and second ends of the arbor tube such that the bottom surface of the inner rim abuts the shoulders, and the face plates are thus maintained at a set distance apart by the shoulders. The hub further includes brush filaments disposed radially about the outer surface of the arbor tube. When the face plates are coupled to the arbor tube with the bottom surface of each inner rim abutting a shoulder of the arbor tube, the filaments have a substantially uniform filament density between the face plates.
The arbor tube may also include a pair of extensions, with each extension extending away from a respective shoulder, and with the face plates mounted on a respective extension. The extensions may be deformed to abut respective top surfaces of the face plates to couple the face plates to the arbor tube. At least one of the face plates may include at least one spike, and the shoulders of the arbor tube may include chamfered portions.
The present invention is also directed to a power brush assembly with brush filaments mounted on an arbor tube and between face plates. The brush filament density is determined by the distance of the face plates from each other, as set by the distance of shoulders provided on the arbor tube. In a preferred embodiment, the brush filaments are formed as a plurality of separate brush sections, each brush section including a retaining ring and a plurality of filaments around the retaining ring. Spacing between the brush sections is set by the distance between the shoulders and the resulting set distance between the face plates. At least one of the face plates may include at least one spike biting into the brush filaments.
Another aspect of the present invention is the formation of a power brush hub with an arbor tube having first and second ends and a pair of opposing locking plates, a locking plate being mounted on each end of the arbor tube. A key-shaped region is defined in each of the locking plates, the key-shaped region having at least a circular portion and a keyseat. A pair of opposing keyseats may be provided in each key-shaped region, and the keyseat may be a rectangular groove. A lip also may be provided in the circular portion of the key-shaped region. Such configuration permits a shaft to positively transmit torque to the locking plate via a key and keyseat system, rather than simply frictional engagement of drive flanges on face plates of the power brush.
In a preferred embodiment, at least one adapter, configured and dimensioned to be engaged in the key-shaped region of the locking plate, is provided. The adapter includes an outwardly extending key shaped to engage within the keyseat of the key-shaped region of the locking plate. If desired, a pair of opposing keyseats may be provided within the key-shaped region of the locking plate, and the adapter may include a corresponding pair of opposing outwardly extending keys shaped to engage within the keyseats of the locking plate key-shaped region. An adapter key-shaped region may be defined in the adapter, shaped to accommodate a shaft smaller in diameter than the locking plate key-shaped region and keys mounted on the shaft.
Yet another aspect of the present invention is a method for positively driving a power brush, the method including: providing a hub comprising an arbor tube having first and second ends and a locking plate mounted on each end, at least one of the locking plates having at least one key-shaped region having at least a circular portion and a plate keyseat; providing a rotary shaft, the shaft having at least one shaft keyseat; and inserting a key in the shaft keyseat and the locking plate keyseat, thereby coupling the shaft to the hub. The locking plate may be adapted for mounting on a drive shaft having a smaller shaft diameter than the circular portion of the key-shaped region of the locking plate by using an adapter in the key-shaped region. The adapter includes an adapter key-shaped region having at least a circular portion and an adapter keyseat. A key inserted in the shaft keyseat and the adapter keyseat couples the shaft to the adapter.
These and other features and advantages of the present invention will be readily apparent from the following detailed description of the invention, the scope of the invention being set out in the appended claims.